A half-dozen parents whose children died or were injured in school told ABC News they were shocked to learn about the kinds of techniques some schools were using to subdue students who were misbehaving.

"All that I was told was that they talk to the students -- you know, try to calm them down," said Foster, whose son Corey, 16, died at Leake & Watts, a school and residential treatment center just outside of New York City. "I didn't know anything about restraint and seclusion therapeutic holds until this happened."

A school surveillance video that Foster shared with ABC News shows her son shooting baskets, and then being shoved into a gymnasium wall, surrounded by a group of school staff, and forced to the ground. For several minutes he is at the bottom of this scrum. A gurney can be seen being wheeled into the gym, where a motionless Foster remains on the ground.

The school told ABC News that the staff behaved exactly as they were supposed to. "Our staff used various de-escalation and re-direction techniques prior to initiating the therapeutic hold, which was performed correctly and in accordance with the state-mandated protocol," said Meredith Barber, director of Institutional Advancement at Leake & Watts. "We regularly train and retrain our staff in TCI (Therapeutic Crisis Intervention), a crisis intervention technique designed by Cornell University."

Barber said she was limited in what more she could say. But she noted that "extensive third-party independent reviews by the police, the District Attorney's office, the medical examiner and state officials support Leake & Watts' own internal investigation and this conclusion: Corey's death was a terrible tragedy." An autopsy ruled Corey's death an accident, saying he suffered "cardiac arrest during an excited state while being subdued."

A school in Massachusetts established to provide an education to those with severe developmental disabilities and behavioral problems, called the Judge Rotenberg Center, has repeatedly come under scrutiny for employing electric shocks to students' arms and legs as a means of improving their behavior. Cheryl McCollins said she was mortified when she realized the school had applied shocks to her son 31 times during a single -- and clearly agonizing -- encounter, even though she had initially agreed in theory to the use of skin shock aversion therapy.

It took 10 years before courts allowed her to make public a video showing the day her son Andre was shocked by school officials, including while he was on the floor with his splayed arms and legs strapped to wooden planks. She showed the video to ABC News and described what she was looking at.

"I see my son being tortured, terrorized by inhumane, criminally insane, out-of-control savages," she said.

Officials at the Judge Rotenberg Center said the treatment was approved both by Andre's mother and by a court official, and the electric shocks have proven effective in improving the behavior of children who are prone to harming themselves or are violent to others. They said the student body at the school is comprised of some of the nation's most troubled children, those who have already failed to succeed in more traditional programs.